Pes Planus (Flat Foot) - Orthopaedics 15 Marks

Definition

• S Das Manual on Clinical Surgery, 13th Ed
• Bailey and Love's Short Practice of Surgery, 28th Ed

Anatomy of the Normal Arch

• Bony architecture - interlocking tarsal and metatarsal bones
• Static stabilizers - spring (calcaneonavicular) ligament (primary static stabilizer of the talonavicular joint), plantar fascia, deltoid ligament
• Dynamic stabilizers - Posterior Tibial Tendon (PTT) (primary dynamic support), tibialis anterior, intrinsic muscles of the foot

• Miller's Review of Orthopaedics, 9th Ed

Classification

I. By Flexibility

II. By Etiology

A. Physiological / Congenital

1. Normal infantile flat foot - physiological before age 6-8 (fat pad in arch)
2. Congenital vertical talus - "rocker-bottom" or "boat-shaped" foot
3. Hyperlaxity syndromes - Marfan's syndrome, Ehlers-Danlos syndrome

B. Anatomical / Structural

1. External rotation of tibia
2. Genu valgum
3. Equinus position of the foot
4. Varus position of the forefoot

C. Acquired

1. Postural / Muscular - weak intrinsic muscles, obesity, prolonged standing (middle-aged flat foot)
2. Posterior Tibial Tendon Dysfunction (PTTD) - most common cause of adult-acquired flat foot deformity (AAFD)
3. Tarsal coalition - calcaneonavicular or talocalcaneal bar causes rigid, painful flat foot (common in adolescents 12-16 years, often bilateral, 1 in 100 people)
4. Inflammatory - rheumatoid arthritis
5. Neurological - polio (flaccid), cerebral palsy (spastic)
6. Post-traumatic
7. Spasmodic flat foot - due to peroneal muscle spasm, often secondary to tarsal coalition

• S Das Manual on Clinical Surgery, 13th Ed
• Miller's Review of Orthopaedics, 9th Ed

Clinical Features

Symptoms

• Medial ankle/foot pain (early) - pain over spring ligament and PTT
• Progressive loss of arch
• "Foot strain" - strain of the inferior calcaneonavicular (spring) ligament
• Lateral ankle pain (late) - due to subfibular impingement
• Aching midfoot and pretibial pain

Signs (Look-Feel-Move)

• Loss of medial longitudinal arch - flattening or even convexity with prominence of the tarsal navicular
• Hindfoot valgus - heel tilted outward
• Forefoot abduction
• "Too many toes" sign - when foot viewed from behind, more than the normal 4th and 5th toes are visible lateral to the heel (indicates forefoot abduction)
• Shoe wear - inner border of heel and sole worn more; inner border of shoe bulges medially

• Localized tenderness over the spring ligament (inferior calcaneonavicular ligament)
• Tenderness along the PTT (medial to medial malleolus, along navicular)

• Limitation of subtalar and midtarsal joint movements (especially in rigid/spasmodic flat foot)
• Single-limb heel rise test - pain or inability to rise on toes on single limb = insufficient PTT; in normal flexible flat foot the arch reconstitutes on tip-toe standing
• In flexible flat foot, arch reconstitutes with toe standing or non-weight bearing
• S Das Manual on Clinical Surgery, 13th Ed
• Bailey and Love's Short Practice of Surgery, 28th Ed
• Miller's Review of Orthopaedics, 9th Ed

Investigations

Radiological

• Weight-bearing X-rays are mandatory:
  • Lateral view: Broken Meary angle (lateral talar-first metatarsal angle) - normally 0°; negative (plantar-directed sag) in pes planus; measured at the talonavicular joint
  • AP view: Talonavicular (TN) uncoverage - indicates forefoot abduction; normally the talus is covered by the navicular
  • Hindfoot equinus on lateral view
• Tarsal coalition signs on X-ray:
  • C-sign and dorsal talar beaking - seen with middle facet (talocalcaneal) coalition
  • Elongated anterior process of calcaneus (on lateral radiograph) - calcaneonavicular coalition
• CT scan - best for evaluating tarsal coalition (3x better than plain X-rays)
• MRI - for soft tissue pathology (PTT integrity, spring ligament tears)
• Miller's Review of Orthopaedics, 9th Ed
• Campbell's Operative Orthopaedics, 15th Ed 2026

PTTD Staging and Treatment (Johnson and Strom Classification)

Stage II Surgical Algorithm:

• FDL or FHL tendon transfer for all patients
• Gastrocnemius recession if equinus contracture present (Silfverskiöld test)
• Hindfoot valgus - medial slide calcaneal osteotomy (Koutsogiannopoulos)
• Forefoot abduction (TN uncoverage >40%) - lateral column lengthening (Evans anterior calcaneal osteotomy)
• Forefoot supination:
  • Stable medial column - Cotton osteotomy (medial cuneiform open-wedge)
  • Unstable medial column - first TMT arthrodesis (Lapidus)
• Miller's Review of Orthopaedics, 9th Ed

Conservative Treatment

1. Observation - asymptomatic cases, especially children (most resolve by age 8-10)
2. Foot orthoses - arch supports with medial heel wedge; do not correct deformity but relieve pain
3. Shoes - stiffer soles, Thomas heel (raised and extended inner border)
4. AFO (Ankle Foot Orthosis) - for symptomatic stage II PTTD; accommodative rigid AFO for stage III
5. Physiotherapy - strengthening of tibialis posterior, intrinsic muscles; Achilles stretching
6. Weight reduction
7. Anti-inflammatory drugs - for inflammatory causes

Surgical Treatment

Flexible Flat Foot (Paediatric)

• Calcaneal lengthening osteotomy (Evans procedure) ± medial imbrication
• 3C osteotomy: sliding calcaneal osteotomy + open-wedge cuboid osteotomy + plantar-flexion closed-wedge medial cuneiform osteotomy
• Avoid calcaneocuboid subluxation during lateral column lengthening
• Extra-articular subtalar arthrodesis (Grice-Green procedure) - historical

Adult Acquired Flat Foot (Stage II)

• FDL/FHL tendon transfer + bony corrections as per staging (see above)
• Spring ligament reconstruction/augmentation (with synthetic tape - gaining acceptance)

Rigid Flat Foot (Stage III / Tarsal Coalition)

• Triple arthrodesis - subtalar + talonavicular + calcaneocuboid joints - gold standard for fixed deformity
• For tarsal coalition: resection and interposition (if <50% of middle facet) or arthrodesis (if >50%)
• Double arthrodesis (subtalar + talonavicular) - alternative
• Miller's Review of Orthopaedics, 9th Ed
• Campbell's Operative Orthopaedics, 15th Ed 2026

Key Points to Remember (Exam Focus)

• Miller's Review of Orthopaedics, 9th Ed
• Campbell's Operative Orthopaedics, 15th Ed 2026
• Bailey and Love's Short Practice of Surgery, 28th Ed
• S Das Manual on Clinical Surgery, 13th Ed